Implement new distutils class `CCompilerOpt`, used for handling
  the CPU/hardware optimization, starting from parsing the
  command arguments, to managing the relationship between the CPU baseline
  and dispatch-able features, also generating the required C headers
  and ending with compiling the sources with proper compiler's flags.

  `CCompilerOpt` mainly used as a helper class for `CCompiler`,
  and doesn't provide any runtime detection for the CPU features,
  instead only focuses on the compiler side, but it generates
  abstract C headers that can be used later for the final
  runtime dispatching process.

* DOC: fix imports and defs to pass refguide checks

Add empty file foo.c at runtime to run distutils config.